Last checkin for the night. This makes tabs fully usable. What's left: Menu item validation code. This will cover all menu items, but most importantly, it will switch the key shortcut for Close Window between cmd+w and shift+cmd+w and Close Tab between blank and cmd+w.

Checking in the underlying prefs structure, and a prefPane, also fir structural integrity. Also including a couple categories to extend a couple Cocoa objects, and some project changes to support building with the bundled prefPanes. Also, added a contrib directory to house user contributed artifacts. To come soon: more prefPanes, and the colorized icon store, with pref-generated notifications to be picked up by toolbars.